I can think of some compelling reasons to shoot with a D800 instead of any previous generation body (D3s, D3, any DX, etc.). WHen the D800 file is reduced to the 12-16 MP size of other bodies, handholdability is the same, dynamic range is much better, color is much better, AF is probably better, ISO performance (both normal and high) is the same or better, and noise characteristics are the same or better.
WIth outstanding glass I can get superb images. With most glass I can get excellent images.
WIth good technique, I get a lot of extra pixels into which I can crop.
Jon Kandel A New York City Nikonian and Team Member Please visit my website and critique the images!